1.56 Mid-Index Finished Single Vision Lens 1) Refractive index (ND): 1.56 2) Abbe value: 38 3) Gravity: 1.28g/m3 4) Diameter: 65 / 70mm 1.60 Hi-Index Finished Single Vision Lens 1) Refractive index (ND): 1.60 2) Abbe value: 36 3) Gravity: 1.34g/m3 4) Diameter: 70 / 72mm